I have a function ( y = f(x) ) that I want to graph in Excel in an xy scatter plot. I usually just make a column of x values and then a column for the y values as a function of the first column, then make the plot based on this set of about 20 points. Is there any way to make a plot straight from the equation, like you would in a graphing calculator?

I hope I'm making myself clear, but if not, let me know and I'll try to elaborate. The function isn't of the type that can have a trend line or polynomial fit, so I can't just do the regression and use that as the function.

I guess I might as well put the equation I'm using:

y = a*x/(1+(a-1)*x) where 'a' is a known constant

BigPete

02-18-03, 11:51 PM

In short, no ... not to my knowledge. Your only hope would be to generate a crapload of points and the try to get excel to apply the right trendline to it so it would return the original equation. I don't think it can create something in that form, though. :(

That's what I figured, but thanks anyway. I was just curious :)

BigPete

02-18-03, 11:58 PM

Originally posted by sdcrym

That's what I figured, but thanks anyway. I was just curious :)

Yeah, I guess I didn't really bother to read past your first sentence or I would have known you knew all that and I could have just said 'no' ... oops. :D

Actually I really need help too and was about to start my own thread. I need to make a graph using specific plot points (x,y) and need to find the linear equation of the best fit line y=mx+b how do I do that?

Its for chemistry. I'm plotting a standard curve for a Bradford and BCA assay in order to find the concentration for an unknown sample. If you were curious.

Well, my response to you depends on how much you know about Excel already. In short, highlight the x and y columns in a spreadsheet, click the make chart button, select xy scatter. Make sure the next page has the x's and y's in the right place. I'm leaving out a lot of details, but you should be able to figure it out. After the scatter plot is displayed, right click on a data point and select add trendline. Make sure linear is selected, then move over to the options tab and check the display equation box.

Sorry for the incoherence... I just finished up my homework and now I'm off to bed :)

Thank you very much! your help is much appreciated. I could figure it out.